Various electro-optical systems have been developed for reading optical indicia, such as barcodes. A barcode is a coded pattern of graphical indicia comprised of a series of bars and spaces of varying widths. In a barcode, the bars and spaces having differing light reflecting characteristics. Some of the barcodes have a one-dimensional structure in which bars and spaces are spaced apart in one direction to form a row of patterns. Examples of one-dimensional barcodes include Uniform Product Code (UPC), which is typically used in retail store sales. Some of the barcodes have a two-dimensional structure in which multiple rows of bar and space patterns are vertically stacked to form a single barcode. Examples of two-dimensional barcodes include Code 49 and PDF417.
Systems that use one or more solid-state imagers for reading and decoding barcodes are typically referred to as imaging-based barcode readers, imaging scanners, or imaging readers. A solid-state imager generally includes a plurality of photosensitive elements or pixels aligned in one or more arrays. Examples of solid-state imagers include charged coupled devices (CCD) or complementary metal oxide semiconductor (CMOS) imaging chips.
FIG. 1 shows an imaging scanner 50 in accordance with some embodiments. The imaging scanner 50 has a window 56 and a housing 58 with a handle. The imaging scanner 50 also has a base 52 for supporting itself on a countertop. The imaging scanner 50 can be used in a hands-free mode as a stationary workstation when it is placed on the countertop. The imaging scanner 50 can also be used in a handheld mode when it is picked up off the countertop and held in an operator's hand. In the hands-free mode, products can be slid, swiped past, or presented to the window 56. In the handheld mode, the imaging scanner 50 can be moved towards a barcode on a product, and a trigger 54 can be manually depressed to initiate imaging of the barcode. In some implementations, the base 52 can be omitted, and the housing 58 can also be in other shapes.
In FIG. 1, many parts for making the imaging scanner 50 may need to satisfy certain flammability requirements. For example, the window 56 may be made from plastic materials, and if a battery is installed in the housing 58 directly with other components, the window 56 and these other components may need to satisfy the flammability requirements of the UL94 standard as defined by Underwriters Laboratories of the USA. The UL94 flammability requirements necessitate the use of plastics of certain kind and of a certain thickness in order for the imaging scanner 50 to pass the UL94 standard. Finding optically clear, elastomeric or sometimes flexible hard plastics with the correct flammability rating that also meet our other specifications (e.g., optical clarity, minimal out-gassing and blooming, or flexural modulus) can sometimes be problematic or many times impossible. The flammability additive can hurt optical clarity and cause significant out-gassing that will cloud optics and affect mechanical properties. Therefore, it is desirable to find a technique that can reduce the flammability requirements for certain components in the imaging scanner 50, such as, the flammability requirements for the window 56.